@@ -185,6 +185,7 @@ struct mpage_da_data {
#define EXT4_IO_END_ERROR 0x0002
#define EXT4_IO_END_QUEUED 0x0004
#define EXT4_IO_END_DIRECT 0x0008
+#define EXT4_IO_END_IN_FSYNC 0x0010
struct ext4_io_page {
struct page *p_page;
@@ -89,6 +89,7 @@ int ext4_flush_completed_IO(struct inode *inode)
io = list_entry(ei->i_completed_io_list.next,
ext4_io_end_t, list);
list_del_init(&io->list);
+ io->flag |= EXT4_IO_END_IN_FSYNC;
/*
* Calling ext4_end_io_nolock() to convert completed
* IO to written.
@@ -108,6 +109,7 @@ int ext4_flush_completed_IO(struct inode *inode)
if (ret < 0)
ret2 = ret;
spin_lock_irqsave(&ei->i_completed_io_lock, flags);
+ io->flag &= ~EXT4_IO_END_IN_FSYNC;
}
spin_unlock_irqrestore(&ei->i_completed_io_lock, flags);
return (ret2 < 0) ? ret2 : 0;
@@ -129,12 +129,18 @@ static void ext4_end_io_work(struct work_struct *work)
unsigned long flags;
spin_lock_irqsave(&ei->i_completed_io_lock, flags);
+ if (io->flag & EXT4_IO_END_IN_FSYNC)
+ goto requeue;
if (list_empty(&io->list)) {
spin_unlock_irqrestore(&ei->i_completed_io_lock, flags);
goto free;
}
if (!mutex_trylock(&inode->i_mutex)) {
+ bool was_queued;
+requeue:
+ was_queued = !!(io->flag & EXT4_IO_END_QUEUED);
+ io->flag |= EXT4_IO_END_QUEUED;
spin_unlock_irqrestore(&ei->i_completed_io_lock, flags);
/*
* Requeue the work instead of waiting so that the work
@@ -147,9 +153,8 @@ static void ext4_end_io_work(struct work_struct *work)
* yield the cpu if it sees an end_io request that has already
* been requeued.
*/
- if (io->flag & EXT4_IO_END_QUEUED)
+ if (was_queued)
yield();
- io->flag |= EXT4_IO_END_QUEUED;
return;
}
list_del_init(&io->list);
Hi, The following command line will leave the aio-stress process unkillable on an ext4 file system (in my case, mounted on /mnt/test): aio-stress -t 20 -s 10 -O -S -o 2 -I 1000 /mnt/test/aiostress.3561.4 /mnt/test/aiostress.3561.4.20 /mnt/test/aiostress.3561.4.19 /mnt/test/aiostress.3561.4.18 /mnt/test/aiostress.3561.4.17 /mnt/test/aiostress.3561.4.16 /mnt/test/aiostress.3561.4.15 /mnt/test/aiostress.3561.4.14 /mnt/test/aiostress.3561.4.13 /mnt/test/aiostress.3561.4.12 /mnt/test/aiostress.3561.4.11 /mnt/test/aiostress.3561.4.10 /mnt/test/aiostress.3561.4.9 /mnt/test/aiostress.3561.4.8 /mnt/test/aiostress.3561.4.7 /mnt/test/aiostress.3561.4.6 /mnt/test/aiostress.3561.4.5 /mnt/test/aiostress.3561.4.4 /mnt/test/aiostress.3561.4.3 /mnt/test/aiostress.3561.4.2 Note that this is the aio-stress program from the xfstests-dev test suite. That particular command line tells aio-stress to do random writes to 20 files from 20 threads (one thread per file). The files are NOT preallocated, so you will get writes to random offsets within the file, thus creating holes and extending i_size. It also opens the file with O_DIRECT and O_SYNC. On to the problem. When an I/O requires unwritten extent conversion, it is queued onto the completed_io_list for the ext4 inode. Two code paths will pull work items from this list. The first is the ext4_end_io_work routine, and the second is ext4_flush_completed_IO, which is called via the fsync path (and O_SYNC handling, as well). There are two issues I've found in these code paths. First, if the fsync path beats the work routine to a particular I/O, the work routine will free the io_end structure! It does not take into account the fact that the io_end may still be in use by the fsync path. I've fixed this issue by adding yet another IO_END flag, indicating that the io_end is being processed by the fsync path. The second problem is that the work routine will make an assignment to io->flag outside of the lock. I have witnessed this result in a hang at umount. Moving the flag setting inside the lock resolved that problem. The problem was introduced by the following commit, which first appeared in 3.2: commit b82e384c7bb9a19036b4daf58fa216df7cd48aa0 Author: Theodore Ts'o <tytso@mit.edu> Date: Mon Oct 31 10:56:32 2011 -0400 ext4: optimize locking for end_io extent conversion As such, the fix should be backported to that release (probably along with the unwritten extent conversion race fix I posted a little while back). I will submit the test case above to xfstests in the near future. Signed-off-by: Jeff Moyer <jmoyer@redhat.com> CC: stable@kernel.org -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html